Forum

[mattb31daytona]

Just finished helping a mate with his new toy a 500 electric start bullet of 2003 vintage - only 4000 miles and been in store since 2008.

Long story short - bike has Boyer electronic ignition and iridium plug - had bike running fine after full re-comissoning service and tidying up wiring after new indicators etc....one fault remained which was petrol seepage from the base filter of tap.Previous owner has removed de-compressor so with duff knee can only use electric start.

Went over tonight to sort tap out as he has MOT booked for tomorrow - he had also bought a couple of new NGK 8ES plugs - re-gapped to 20 thou / .5mm as per book replaced and pressed starter which turned and engine emitted a great metallic noise - gingerly tried again making sure clutch fully home bike started but then same noise engine switched off - realised we had been trying to start without using choke so choke closed tried again engine started no noise but not running smooth as previously.

Lots of head scratching - only difference was change of plug .....replaced with original iridium plug ....pressed started and fired instantly no noise and ran smooth - tried this several tines and same each time.....THE QUESTION IS WHY?

The Boyer is the electronic one supplied by Hitchcock's in 2009


Any ideas?

Matt

[Norm]

Well for starters your sprag is on its way out, is this a cast iron or an Electra X if cast iron refit the decomp and get used to kickstarting it, remember there is a reason why it was parked up Po new the sprag was starting to fail

[Leon Novello]

As Norm says. One backfire / kickback now, and there will be a chaincase full of rubble.

[Thack]

You haven't given us the full spark plug number. Is it possible the replacement plug was too long, and hitting the piston?

[Leon Novello]

There is only the B which is the thread 14mm, the E is the reach 19mm and the S stands for Standard 2.6mm electrode. If there is no R it means there is no Resistor. According to my NGK Bible. I`d say the plug is correct, except maybe the heat range could be fiddled with up or down; numbers going down down, the plug is in a hotter range.

[Thack]

Ah yes, I've just checked the NGK numbering system. As Leon and Richard say, the plug must be the right length. I can't understand why the other plug caused that terrible metallic noise, unless the engine was suffering detonation. And quite honestly I don't think that's going to happen with a cold engine - you need some pretty extreme conditions.



Sorry - I can't cast any light on the mystery. Except....



Norm: is it right that a knackered sprag can make such a din? I thought they just slipped, although I don't have the benefit of your experience.

[Norm]

Thack you have no idea the noise a sprag can make, in particular a kickback you step back and expect there to be nothing left in the bottom of the cases except a huge hole and oil everywhere. If the gears break the noise can be grinding/crunching,and locking up, if the bearing locks up it can be a whirring/dragging sound you think of it and a sprag can make it and each time it makes a noise you know it is going to cost you money